Telephone-exchange system.



EDVAR'D HINRICHSEN, GF .NEW YORK, E. Y.,

flamante flies Easy ai, ma.

tain new and useful Improvements in Tele` phone-Exchange Systems, of which the following is a full, clear, concise, and exact scription.

This invention relates to telephoneeX- change systems, and more particularly te such systems of the cent-ral energy type.

It is an object of this invention to provide a telephone exchange system inl Whi it is impossible to connect a source of ringing current to a Aline previously7 taken for use.

Another object of this invention is toprov vide a telephone exchange system in' which it is impossible to connect an operators telephone set to a busy line.

Still another ,object of this invention the provision ofmeans operated upon com nection of any link circuit with a busy line to signal the operator that the link has been connected to a busy line.

In accordance with this invention, there is lprovided a telephone exchange system com ,prising link connecting circuits, the talking lstrands of each of which vare normally open.

Associated with each end` of cach link circuit is a relay forclosing the normally open talking strands thereof, this relay being 2ontrolled by a second relay Whose circuit-is completed when the appropriate end of the link is connected to an idle line. A third relay associated with the link'circuit operates to prevent the operation of the first and second relays if the link is connected to a busy line. In the calling end of the link circuit, the relays cooperate to control the application of a source of ringing current to called lines. Each end of the link circuit is provided with means for signaling the operator whenever either end of the link circuit has been associated with a busy line.

' For a more complete understanding of this invention reference shouldf'be made to the accompanying drawing wherein is illustrated a telephone exchange system showing one embodiment of the invention and comprising the usual subscribers stations, A-

S eclfcetion of Lette-'ix scrilier 'l., wishing to converse With subscriber B, 'anais the opera-tor in the usual manner. ".lhe operator, answering, inserts answering plug into a jack of the calling incline of line. relay 7, contact i' il, ring contacts of the jack Want l@ of relay il, Winding ay 5, Contact 13 of relay le and' t. ground. Relay 5, in optes a locking circuit Afor itself operation of cutotl relay' 9 The operating circuit for relays may be traced from battery 20, rough supervisory signal 2l, Winding of ela ll, locking winding 22 of relay 5, con-l yact 2?) thereof. sleeve contacts of the answernv pirg and jack, and the Winding of cut` n re. a l' 9 to ground, Cutoff relay Qin op- .rating disc-:nnects the line relay 7 from the Jine, and relay il in operating closes normally open contacts in the talking strands of the answering end of the cord' circuit. 'ince subscriber A has initiated the call and the receiver is the switclrhool, supervisory relay 25 will be operated upon the closure of the normally open contacts inthe talking strands of the cord. Supervisory relay in operating`r causes the operation of listening rl wliich connects the operators telephone set across the talking 'i ic cord. .The resistance of the ning relay 2G is such that i shunts supervisory signal 21, therebyl preventing its operatic The operator, "1 1 i of subscriber B, inserts the calling plug into a jack of Bs line, causing the operation of relay 30, the energizing and locking circuits for this relay 'oeing similar to that hereinbefore traced for relay 5 associated with the l answering end of the cord circuit.l The opl eration of relay 30 causes the operation of relays 3l, 32 and 33 and supervisory signal 34. The circuit including these relays and the signal may be traced from battery 35, through supervisory signal 34, Windingof relays 33 and 32, the locking winding and Contact 3G of relay 30, sleeve contacts of the calling plug and jack, and the `winding of cutoti` relay 31 to ground. Cutoi relay 31 in operating disconnects the line relay of Bs line from the line. Relay 32 in operating closes normally open contacts in the talking b the operation of relay 5 overamay be trace-fl from battery 6 that the wanted line is thatJ stran'ds'ol the calling end of the cord circuit. Relay 33 in operating causes the release of liste-ning relay disconnecting the operators telephone set from the talking strands of the cord, and substitutes forthe wind-ing of rela-y 2G a resistance 37 which shunts supervisory signal .21 which remains 33 also connects, through'the operation of relay n source of 'ringing current- 39 tothe called line.1 the source 39 being connected to thering strand of the -cord cireuitvbael: ofthenori'niil open con I tact thereof, and4 ground being connected'to "thereof,

relay in a manner well understood, to

tip strand bsck'of the' normal open eontnct Relays 40 and 4 1 cooperate with control the disconnection-of the source of ringfingT current from the called line upon vthe Vre'nior-fil of the receiver therein; from the switch hook; As soon as the ringing current is-reinoved vtrom the called line,supervisory relay #t5 operates7 retiringsupervisory igual fiel. llhen the conversation is finished, both and B restore 'their respective receivers to the switch hoolncausing the release o'r' superliisory relays 25 and 4:5, whereupon supervisory signals 21. and Br operate to furnish disconnect signals. Removal of the plugs from the jack permitsv all vapparatus to return to noru'ialeodition.

ForjronVenience and sinipliciti-Qonlr one cord cirfuilhzislieen shown' in the-drawing. It to hev understood, 'limiet-H, that nt each' operutors position, there -willhe located' u plurality of cord Circuits like that shown in 'the d raw in gr Agsuniing that siil'iscrihers A und l), V.have heen connected togetlie for conversation h y ineaiis or the eord cireiutiiu the niannr-r iiereiniiefore desrriheland assuming fun ther that an operator in attempting to lisin on the eon\'r.r\:ation 'ts the g the coton r ted, opening thev he. f oril ei i si .if z lthc calling plug there-:n in the jur-l of- Bs line, the potential of the slet-.rcs or all of the jacks associated with lines A and )f3-throughout the hoard will he raised. Therefore, when an answering plu;r of :mother (tord circuit-is plugged .into :i jack :issoiizitx-,d with Ais.` line, relay 14 of the seeond cord circuit will he energized over'a cirvcuit' from hatten-y 20, supervisory signal 21,

- second ourll circuit.`

winding4 'of relay ll, lockingwinding 22 and rontact. '-25% of' relai' sleeve contacts` of the answering' pluLr and jarlc. sleei'e contacts of i and second unswering plug, (in the second cord iding' of relay 14 of thiil to ground. The operazn the second cord :ircuit tact of thil cutoff rela'y-l.'

causes supervisory signal 2l of the'se'rond cord circuit to flash intermittei'itly, signifi.'- infg to the operator that the second cord eircuit has been connected -with the line already taken for use. This circuit for this super. visory relayy 21 may be traced from battery 20, supervisory signal 21,;1lteinatecontnct of relay :14 and interruptor l5, to grouml. In n like manner,'if the answering plug had. been'connected to :i second 'jack associated with Bs line, supervisory signal 2L of the' 'second cord elreuit woulclbe flashed intermittently'. Sincerelny oftheseconfl cord circuit cannot operate, it is impossible to' connect the operators telephone set with the existing telephone' coiuieetion. seen', therefore, that by the use of n telephone lexchange system ei'i'ihodi-'in'g the present. inrention, it is' impossible to connect, an operator-s Atelephone setto assubscribers. line which had been' previouslyl -talien for use.'

Relays 30 and 47 associated with the callingV end of the' cordcircuit Correspond to relavs 5 and' 14 associated with the answering eu'd, and operate in thesnnie mannen It uiill he: recalled that relay 3S, which connect-s the.

source of ringing-Current. *39 to the.' e-iillcd line` iscontrojlled by relay 30j -It willnow lac. Shown how'it is impossihleto connect the niree of ringingcurrent to a line already laken Vfor use..

`When either.- the answering or-the callingv 'i plug of the cord eireuit C isinserted inl the iai-.lc oflls-line',- the cutoff relay 3 1 thereofv t vwill be? 'will he rnicrated. -Shoulduthe.operator iiisert the culling plug of a seeonrl cori'l'ciri-.uit

Vinto another Yj'uukfassoeiutei-l with )ris lille,v

`thrr energizingcircuit `for-relay 30 of the;

lt is to he noted that-it thesystcin is notV to he equipped for furnishingV aA .signal to the operator, the intr-.rrupter l5 rnajyhedisliensed with and this coniiection'run direct to ground. v

l-Vhile :i plurz'ilit)r of batteries' are Shown in the drawing` it is to he understood that a'.

signal fl of the .s rond oord Singh: connnon:battery may .he substituted therefor,l and such is the usual practice.

ll'hal is rlaiiued is: l. ln :i telephone exithnngfe s YSt-eiu, suhserihers" lines termina-ting ai. a Central silice,

tion control tor rendering said relay in-4' dependent of the energizing circuit, and a second relay operating upon energization of said first named relay for closing the talking strands of said link circuit.

2. ln a telephone exchange system, subscribers lines terminating at a central oice, a link circuit thereat for interconnecting said lines, normally open talking strands tor said link circuit, a relay energized over a circuit including a portion of one strand of said link upon connection ci said link with a line, a locking circuit for said relay for rendering said relay independent of the energizing circuit, and a second relay included in the locking circuit and operating upon energization of said first named relay for closing the talking strands of said link circuit.

3. In a telephone exchange system, sub` scribers lines terminating'at a central office, a link circuit thereat for interconnecting said lines, normally open talking strands and a third strand for said link circuit, a relay energized over a circuit including a portion. of a talking strand of said link upon connection of said link with a, line, a locking circuit for said relay including a portion of the third strand of said link com.- pleted-upon energization of said relay, and a second relay opera-ting upon energization of named relay for closing the talking strands of said link,

4. In a telephone exchange system, subscribers lines terminating at a central office, a link circuit 'thereat for interconnecting said lines, normally open talkingstrands and a third strand for said link circnit, a relay energized over a circuit inclhdiiig a portion of a talking strand of said link upon connection of said link with a line, a locking circuit for said relay includinga portion of the third strand of said'link cornpleted upon energization of said relay, and a second relay in the locking circuit of said first named relay operating upon completion of the locking circuit to close the talking strands of said link.

5. In a telephone exchange system, subscribers lines terminating at a central office, a link circuit thereat for interconnecting said lines, normally open talking strands -for said link circuit, electromagnetic mechanism operating when the answering end of said link is connected with a calling line to close` the `talking strands of said link, operators telephone set, a listening relay for including said telephone set in telephonie connection with the calling line, a circuit for said listening relay controlled lfrom the calling substation and closed after the closure of the talking strands of said link, Whereby said telephone set is connected with the calling line, and relay mechanism responsive to the connection of the calling end of said link with another line for opening the circuit of said listening relay, thereby disconnecting said telephone, set from the line.

(i. In a telephone exchange system, a telephone line termina-ting in a plurality of switching terminals at a central oliice, a plurality of link circuits thereat having cooperating switching terminals, each link having normally open talking strands, relay mechanism operating when a link circuit is connected with a, switching terminal of the line for closing the talking strands of said link and for altering the electrical condition of the switching termina-ls of the line, a relay associated with each link circuitirresponsive to the original electrical condition of the switching terminals of the line but responsive to the altered electrical condition thereof, said relay of the connected link circuit being rendered inoperative by the 4operation of said re'lay mechanism, said `relay of a second link circuit operating when the second link is connected with another switching terminal of the line for preventing the operation of said relay mechanism of the second Alink thereby preventing the closure of the talking strands of the second link.

7 In a telephone exchange system, a telephone line terminating inV a' plurality of switching terminals at a central oice, a plurality of link circuits thereat having coperating' switching terminals', mechanism opv eratmg when a link circuit 1s connected with a switching terminal of the line for altering the electrical condition of the switching terminals thereof, a relay associated With each link circuit irresponsive to 7the original electrical condition of the switchingy terminals of the line but responsive to the. altered l:electrical condition thereof, the operation 10 said mechanism rendering said relay of the connected link inoperative, a signaling device, and interruptor mechanism, said relay of a second link responding to the altered electrical condition of the 'switching terminals when tie second link is cor.- nected-vzith another' witching terminal of `the line for includingthe interrupter mechanism in circuit with said signaling device to furnish a signal denoting that the second link has beenconnected to a busy line.

8. In a telephone exchange system, subwith ;i line. iiiezins forreiiileriiig Siiid'relny Y onli" relay operating upon energizntion of Suid lirSt-iiziiiied reluyfor closing the-normal liii=:i l s'iii tlie tzilkingvstrnnds ofthe siiid liiik, n. soince of riiigin'g'riirijent adapted to he v.ci'innected fof one of the.. tiilking-strnnds hack controlled hy Sfiid tir-st-ngiinedreliiy.for connei-tuigr sind sour-ee. 'to the tziill'cing strand of the link.

El.- In' ii telephone exchange -Systeiin 4tele-V plionje liuenterriiinn'ting atir centi-:il ollice,

'suiidfsoiiree to' the talking strands hack ofi the.. liroiik;l tlieieii'i.. und relay' mechanism pri-renting tlieclosiireI ofxtl-io. tnlking strands .zinoih'er linkvr is :ilrezifdy connected, thereby preventing the 'applicationof `ringing cur rent to :i line pi'erioualy taken for use.

l0.. ln n telephone e. \-'ch:i nge System.v :L tele.- phone line. -fte'ri'ninoting-1.in in pliirnlity of `sii-itchingr tciiiiiiinls :it zi central olliee, ai. plui'zilityof link-circuits the-rent having coperzitiiig switching' teiiiiinii'ls'f. n vielziy aseo ciuted with tlinriilliiigend ofieiich link. Said link iconnected `with :LMV-itching tern'iinzil .of the line tonlter the electrical conditionof `the,`. \'itching tei'u'iiiizilnof siiidiline, :i-Soiii'ce' nt, :ind: 'n vrelay' 'o'iieriiting 'upontho eiieVgiYlJtiouQf .the Alirnt mentioned ijelny vfor-coniipeting sziid Si'iiirgji. to Suid-'line tliroiiglrtlic ciilliijig end'jf the link. the tiret ving. iircsponsire to tl'ie valtered electrical coii- `iition` otsnid line irlieiin;seeond'link is eonnei'fted njitli another switching teiiiiiniil of A#nid line., irliei'elruthe ;i'pplici'rion of ringing .iiirciit to :i line pici'.i oii spl taken 'for use is preriiiiteil. v

ll. .l-n -ri tilei'ilionir excluinge system, sul. 'scrilu'iijs` lineA teriiiiiiutiiig zit n centr-nl oi'ce` :ir link ci "iii liereiit for interconnecting i ii.irin: i ll ope ii talking sti-:ind iii .Y (Il iifiined relay f pon exierg i'ziit'ioii o f or closing said nor r niiilly opciitilking strand.; :ind-a loczilvloeking'eircuit independent of substation control of the! link Vcircuit"upon-connection thereof' with :L line, :i loc-(il locking circuit for the relay established upon the en ei'gizntiivonY independent of the encigizii'igcircuit, :i sec- 'closing the talking strand of the link ircuit.

13. In :i teleplionefexclninge system, subscribers lines vterminating at a central-omge.

:i link circuit. tlierezitfor intereonmeeting.nevv

lines. @zich link Vcircuit lizivin'gxa normally open talking strz'indf-a rieliiy'energigedoyer :i circuit including n' portion of nl .tlk-ing.

thereof u'i'tli 'n line. :i $econdrelzi-y operating upon the. energizat-ion of the Iirst-nziined irelny for closing the-talking -strand of the link fcirciiit'. :ind a lociilfloekiiig joli-'cuit .indei pendent of siihstiition lc ontrol'for the second '75 strand of thellinkcirciiit upon 'connection' 14; In n telephone-'ekohzinge sytinussvub.'

serilierbf lines terniiniitiiigatfn*central oflice. :i link circuit tlierezit forintrconneetii'ig the lines, euch link'circuit-having.nfnormally open tidkii'ig strand, :i relziy energized over :i circiiit including .a portion of nftfilking strand of the link eircuitrupon Connection,

thereof with ii line.. n local-looking circuit for the relay estzihlisliedupon.tlielenergiza# tion thereof, and :tsecondfgelaly 'ign'thelooking ciieiiitoperiiting upon theclosur'thi of for closingtlie tzilkingstrnnd ofthe-lilik circuit.. Y I I' 15. In n telephone-oxen ng 'System`- subsci'ihers inii l ly open talking strand', rel' l' ii'ii'illy open tnlli'ii'ig s ti'ani'l5'21`ii operat-NS mentioned relay of :i -Secmiiil' link ciieuitlietelephone set,-V zi' listening -relnyi energizedp- 'upon the ifli'isiiiejof the talking Strand for .lines te'riiiiiniting 'ait-1r centriil-'ol'cef :i linl circuit thereiit .foi-. interconnecting the. lines, 'eiielr-liiikei'itzuit'ha tion of the other end ot the linkoireii'itwitli' 1'/,iiig'l'lie listening sifriwrzf" linen tei'ii'iiiniting at iii rentrait c-lliee in n pliirzilitj.' ol' tei'iiiiinilsfr plu'izirlityx of linkt irciif for interconneetingthe ines, euch'` linkl t f n'.normnlly'open ii-rel'y ziocinted witl :icl connecingv the" Source talking stijgiinl, a third'ireliiy VAfor eziolilinlfz circuit operating upon eonnection @of-" the l'iiik with a line .for causing. the ope'riition of the first u ,nd second mentioned releiys, :ind' means-operating upon connection-'0f the link with the. line to prevent the operation-of the third relay of another. link circuit when Y connected with the same line; i 17. In a telephone exchange system. siihscrihers lines termine-fing ut a central office y manges i1 a plurality of terminals, a plurality of link circuits for interconnecting the lines, a. source of ,ringing current, a relay associated with each link circuit for connecting the source of ringing current with the talking strands" thereof, a second relay for each 'link circuit operating upon connection of the link with the line for causing the operation of the first-named relay, and means operating .upon connection of the link with the line to prevent the operation of the second relay of another link circuit when connected with the same line.

18.` In a telephone' exchange system, subscribers lines terminating at a central oliice in a plurality. of terminals, a plurality of link circuits for interconnecting the lines, a tsource of ringing current, a relay associ ted with each link circuit for connecting the source of ringing current with the talking strands thereof, a, second relay for each linkv circuit operating upon connection of the linkl with the line'for causing the operation of the first-named relay, and a relay operating upon connection 'of the link with the line to prevent the operation of the second relay of another link circuit when connected with the saine line. Y

19. In a telephone exchange system, subscribers. lines terminating at a central ollice in a plurality of terminals, a plurality ot link circuits for interconnecting the lines, a Source of ringing current, a relay associated with each link circuit for connecting the source of ringing current with the talking strands thereof, a second relay for each link circuit operating upon connection of the link with the line for causing the opera-.

tion of the first-named relay, and a relay normally associated with the line circuit operating upon connection of the link with the line to prevent the operation of the second relay of another link circuit When connected with the same line.

in Witness whereof, I hereunto subscribe 

